linux-user/sparc: Put address for data faults where linux-user expects it

linux-user/sparc: Put address for data faults where linux-user expects it

In the user-mode-only version of sparc_cpu_handle_mmu_fault(),
we must save the fault address for a data fault into the CPU
state's mmu registers, because the code in linux-user/main.c
expects to find it there in order to populate the si_addr
field of the guest siginfo.

Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Riku Voipio <riku.voipio@linaro.org>